Variety of methods are known to form a loop of a flexible strip such as a carcase or breaker ply to form part of a pneumatic tire. One of these methods is to form a loop of a flexible strip by joining together opposite end portions of an initially elongated flexible strip without use of a cylindrical drum. Such a method is disclosed in, for example, Japanese Provisional Patent Publication No. 55-91651.
In the loop forming method taught therein, positioning plates are attached to opposite end portions, respectively, of an elongated flexible strip, whereupon the positioning plates are driven to move until the flexible strip is deformed into loop form and the end portions of the strip are moved into predetermined positions having their respective edges slightly spaced apart in parallel from each other. The end portions of the strip thus deformed are thereafter joined together along the edges thereof. One of the problems encountered in this conventional loop forming method is that the final positions of the end portions of the flexible strip are determined by the movements of the positioning plates. If one of the positioning plates happens to abut to the edge of the end portion of the strip carried on the other positioning plate, the disturbed end portion of the strip is caused to deform irregularly. Another problem is that the end portions of the strip can not be moved into the predetermined positions with satisfactory accuracy due to the errors inevitable in moving the positioning plates into desired positions. Because, furthermore, of the fact that the respective positions of the end portions of the strip are corrected on a conveyor, not only an unduly large force is required for deforming the strip but the end portions of the strip are liable to deform irregularly.
The present invention contemplates elimination of these problems encountered in prior-art loop forming methods.